AMETHYST documents outcomes in glucocorticoid-refractory macrophage activation syndrome complicating Still’s disease

The AMETHYST retrospective cohort study examined treatment patterns and outcomes in glucocorticoid-refractory macrophage activation syndrome (MAS), a life-threatening complication of Still’s disease. Investigators reviewed records from eight sites in Europe, Canada, and the United States, covering January 2012 through March 2023. Among 64 patients, 55 had systemic juvenile idiopathic arthritis and nine had adult-onset Still’s disease; 53 were children at the index MAS episode, with a median age of 7.0 years.

All patients received glucocorticoids, with 48 (75%) also receiving anakinra and 33 (51.6%) ciclosporin. Complete laboratory remission, defined as normalization of seven prespecified parameters, occurred in seven patients (10.9%); partial laboratory remission, defined as normalization of at least three parameters, occurred in 41 (64.1%). Investigators assessed complete and partial clinical responses in 24 (37.5%) and 26 (40.6%) patients, respectively. Glucocorticoids were tapered in 50 patients (78.1%), at a median of 39.9 days.

MAS recurred in 20 patients (31.3%). Seven patients (10.9%) died, while estimated one-year survival was 93.75%. These findings describe substantial residual disease burden in a predominantly pediatric, treatment-refractory population. The retrospective design and small adult subgroup limit interpretation, and the reported outcomes do not establish comparative treatment effectiveness. Only the abstract was available, limiting assessment of follow-up, treatment-specific outcomes, and adverse events.